<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
		<script>
		 var n=prompt("input:");
		 if(isNaN(n)){
			 alert("输入错误");
		 }else{
			 var a=parseInt(n);
			 alert(a);
		 }
		 
		 //var str="4+5";
		 var str="alert('We change lives!')";
		 var c=eval(str);
		 alert(c);
		</script>
	</head>
	<body>
	</body>
</html>
